Parallel Channels for Motion Feature Extraction in the Pretectum and Tectum of Larval Zebrafish

Abstract

Summary: Non-cortical visual areas in vertebrate brains extract relevant stimulus features, such as motion, object size, and location, to support diverse behavioral tasks. The optic tectum and pretectum, two primary visual areas in zebrafish, are involved in motion processing, and yet their differential neural representation of behaviorally relevant visual features is unclear. Here, we characterize receptive fields (RFs) of motion-sensitive neurons in the diencephalon and midbrain. We show that RFs of many pretectal neurons are large and sample the lower visual field, whereas RFs of tectal neurons are mostly small-size selective and sample the upper nasal visual field more densely. Furthermore, optomotor swimming can reliably be evoked by presenting forward motion in the lower temporal visual field alone, matching the lower visual field bias of the pretectum. Thus, tectum and pretectum extract different visual features from distinct regions of visual space, which is likely a result of their adaptations to hunting and optomotor behavior, respectively. : Wang et al. show that the zebrafish optic tectum and pretectum extract visual motion features associated with hunting and optomotor behavior, respectively. The tectum preferably represents small stimuli in the upper nasal visual field, whereas the pretectum is biased toward larger stimuli in the lower visual field. Keywords: receptive fields, motion vision, pretectum, optic tectum, zebrafish, calcium imaging, optomotor response, topography, optic flow